The invention relates to face mill cutter head assemblies of the continuous indexing type adapted for use in gear cutting machines. The cutter head is designed to receive tools characterized by their front face portions requiring no resharpening. More particularly, the invention relates to improvements in cutter head assemblies of the aforesaid type whereby the front face portions of the cutting tools mounted therein may be preserved during resharpening. In addition, the invention provides for a method for designing such cutter head assemblies.
The use of cutting blades where sharpening stock is removed from the shank portion in a fashion that preserves the front face portion of these tools is well known in the art of metal cutting (for example see U.S. Pat. No. 1,648,380). Practical advantages of using such blades are also well known in the art of gear cutting as discussed in U.S. Pat. Nos. 3,961,403; 4,060,881; and East German Pat. No. 112923 (1975). Recent application of blade coating processes has resulted in improved tool performance and tool life. Cutter head designs which permit the use of blades of the above-mentiond type possess the further advantage of benefiting from such coating processes despite repeated sharpenings. Appreciable savings in productivity and tool costs can be realized as the original coating is preserved on the tool face for the entire service life of the tool.
It is also known to use bar-stock type blades of generally quadralateral cross-section in face hobbing type cutter heads. The use of such blades where sharpening stock is taken from the shank portion obviates the need for corrective radial adjustment subsequent to resharpening as is common in face mill hobbing cutters using conventional blades. A head design of this type is disclosed in U.S. Pat. No. 3,760,476. While this design permits the use of blades with sharpening stock in the blade shank portion, special requirements of cutting edge alignment inherent to the hobbing process have hitherto precluded the use of sharpening processes which preserve the face portion of the tool.
It is common practice in the manufacture of bevel and hypoid gear sets according to the face hobbing process to generate mating members on the basis of a theoretical crown gears. When edges of cutting blades for both members coincide with respect to a plane normal to the longitudinal tooth curve of the imaginary common crown gear, the members can then be generated conjugate to each other. Failure of the cutting edges for both members to coincide may result in undesirable mismatch of mating gear teeth. Heretofore, it has been common practice to maintain the correct disposition of cutting edges in the face hobbing process by grinding the front faces of cutting blades.
It is an object of this invention to disclose a novel cutter assembly of the face hobbing type for the production of conjugate bevel and hypoid gears when utilizing bar-stock type blades having front faces preserved during resharpening.
Another object of this invention is to disclose a cutter assembly of the above mentioned type wherein a given range of job requirements may be accomodated and deleterious tooth mismatch avoided without necessitating corrective adjustment of cutting blade faces.
Other objects and features of this invention will become apparent in the detailed discussion which follows. In that discussion reference will be made to the accompanying drawings as briefly described below: